/* ========================================
   I-Bond Calculator — Design System
   ======================================== */
:root {
  --bg-primary: #0f0f1a;
  --bg-secondary: #1a1a2e;
  --bg-card: #16213e;
  --bg-card-hover: #1c2a4a;
  --text-primary: #e8e8f0;
  --text-secondary: #9a9ab0;
  --text-muted: #6b6b80;
  --accent-purple: #6c63ff;
  --accent-purple-glow: rgba(108, 99, 255, 0.3);
  --accent-green: #00d68f;
  --accent-green-dim: rgba(0, 214, 143, 0.15);
  --accent-red: #ff6b6b;
  --accent-red-dim: rgba(255, 107, 107, 0.15);
  --accent-gold: #ffc857;
  --accent-gold-dim: rgba(255, 200, 87, 0.15);
  --accent-blue: #4da6ff;
  --border: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(255, 255, 255, 0.15);
  --radius: 12px;
  --radius-sm: 8px;
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --shadow-glow: 0 0 30px rgba(108, 99, 255, 0.15);
}
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { font-size: 16px; scroll-behavior: smooth; }
body { font-family: var(--font-sans); background: var(--bg-primary); color: var(--text-primary); line-height: 1.6; min-height: 100vh; }
.mono { font-family: var(--font-mono); }

/* ---- Loading ---- */
.loading-overlay { position: fixed; inset: 0; background: rgba(15,15,26,0.95); display: flex; align-items: center; justify-content: center; z-index: 1000; backdrop-filter: blur(8px); }
.loader { text-align: center; color: var(--text-secondary); }
.loader-ring { width: 48px; height: 48px; border: 3px solid var(--border); border-top-color: var(--accent-purple); border-radius: 50%; margin: 0 auto 16px; animation: spin 1s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.error-banner { background: var(--accent-red-dim); color: var(--accent-red); padding: 12px 24px; text-align: center; font-size: 0.875rem; }

/* ---- Header ---- */
header {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 32px; height: 56px;
  background: rgba(15, 15, 26, 0.88);
  backdrop-filter: blur(16px); -webkit-backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; }
.header-inner h1 { font-size: 1.1rem; font-weight: 700; letter-spacing: -0.01em; }
.accent { background: linear-gradient(135deg, var(--accent-purple), #a78bfa); -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text; }
.subtitle { display: none; }

/* ---- Navigation ---- */
.top-nav { display: flex; gap: 2px; margin: 0; }
.nav-btn { background: transparent; color: var(--text-secondary); border: none; padding: 6px 14px; border-radius: 8px; font-size: 0.875rem; font-weight: 500; cursor: pointer; transition: all 0.15s; }
.nav-btn:hover { background: var(--bg-card); color: var(--text-primary); }
.nav-btn.active { background: rgba(108, 99, 255, 0.15); color: var(--accent-purple); }

/* ---- Tabs ---- */
.tab-view { display: none; animation: fadeIn 0.3s ease; }
.tab-view.active { display: block; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(5px); } to { opacity: 1; transform: translateY(0); } }

/* ---- Settings Accordion ---- */
.settings-accordion { margin-bottom: 20px; background: transparent; border: none; border-radius: var(--radius-sm); transition: all 0.2s; }
.settings-accordion[open] { background: var(--bg-card); border: 1px solid var(--accent-purple); box-shadow: var(--shadow-glow); }
.settings-summary-bar { padding: 6px 0; display: flex; justify-content: space-between; align-items: center; cursor: pointer; list-style: none; }
.settings-accordion[open] .settings-summary-bar { padding: 12px 20px; }
.settings-summary-bar::-webkit-details-marker { display: none; }
.settings-summary-content { display: flex; align-items: center; gap: 8px; }
.settings-summary-icon { display: none; }
.settings-summary-text { font-size: 0.8rem; color: var(--text-muted); font-weight: 400; }
.settings-summary-action { font-size: 0.8rem; color: var(--text-secondary); font-weight: 500; display: flex; align-items: center; gap: 4px; text-transform: none; letter-spacing: 0; }
.settings-accordion:not([open]) .settings-summary-action { color: var(--accent-purple); }
.accordion-chevron { transition: transform 0.2s; font-size: 0.7rem; }
.settings-accordion[open] .accordion-chevron { transform: rotate(180deg); }
.settings-accordion-content { padding: 0 24px 24px 24px; border-top: 1px dashed var(--border); margin-top: 8px; padding-top: 24px; }

/* ---- Main ---- */
main { max-width: 960px; margin: 0 auto; padding: 32px 24px 48px; }

/* ---- Modal ---- */
.modal-backdrop { position: fixed; inset: 0; background: rgba(0,0,0,0.6); z-index: 900; display: flex; align-items: center; justify-content: center; backdrop-filter: blur(4px); }
.modal { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); padding: 28px; width: 90%; max-width: 560px; box-shadow: var(--shadow); }
.modal-header { display: flex; justify-content: space-between; align-items: center; margin-bottom: 20px; }
.modal-header h2 { font-size: 1rem; font-weight: 600; color: var(--text-primary); }
.modal-close { background: transparent; border: none; color: var(--text-secondary); font-size: 1.2rem; cursor: pointer; padding: 4px 8px; }
.modal-close:hover { color: var(--text-primary); }

/* ---- Controls ---- */
.controls-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 20px;
}
.control-group { display: flex; flex-direction: column; gap: 6px; }
.control-group label {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 0;
}
.slider-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 0;
}
.slider-row input[type="number"] {
  width: 72px;
  background: var(--bg-primary);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px;
  color: var(--text-primary);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  outline: none;
  transition: border-color 0.2s;
  text-align: center;
}
.slider-row input[type="number"]:focus { border-color: var(--accent-purple); }
.slider-row input[type="range"] {
  flex: 1;
  -webkit-appearance: none;
  height: 5px;
  background: var(--bg-primary);
  border-radius: 3px;
  outline: none;
}
.slider-row input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 16px; height: 16px; border-radius: 50%; background: var(--accent-purple); cursor: pointer; box-shadow: 0 0 6px var(--accent-purple-glow); }
.helper {
  font-size: 0.75rem;
  color: var(--text-muted);
  display: inline-block;
  font-weight: 400;
  text-align: right;
}

/* ---- Chart ---- */
.chart-section { margin-bottom: 24px; }
.chart-section h2 { font-size: 1rem; font-weight: 600; margin-bottom: 12px; color: var(--text-secondary); }
.chart-subtitle { font-weight: 400; font-size: 0.85rem; color: var(--text-muted); }
.chart-container { background: var(--bg-secondary); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px; overflow: hidden; position: relative; height: 300px; }
.chart-container canvas { width: 100% !important; height: 100% !important; }
#history-chart { width: 100%; height: 260px; }
.chart-loading { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; color: var(--text-muted); font-size: 0.85rem; background: rgba(26,26,46,0.8); }
.chart-legend { display: flex; gap: 20px; justify-content: center; margin-top: 8px; }
.legend-item { display: flex; align-items: center; gap: 5px; font-size: 0.75rem; color: var(--text-muted); }
.legend-swatch { width: 14px; height: 3px; border-radius: 2px; }

/* ---- Hero Dashboard ---- */
.hero-dashboard { background: var(--bg-card); border: 1px solid var(--accent-purple); border-radius: var(--radius); padding: 16px 24px; margin-bottom: 24px; display: flex; flex-wrap: wrap; gap: 16px; align-items: center; justify-content: space-between; box-shadow: var(--shadow-glow); }
.hero-stats { display: flex; align-items: center; gap: 16px; flex: 1; min-width: 280px; justify-content: center; }
.hero-stat { text-align: center; }
.stat-label { display: block; font-size: 0.75rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 4px; font-weight: 600; }
.stat-value { display: block; font-size: 2rem; font-weight: 700; line-height: 1; }
.ibond-stat .stat-value { color: var(--accent-purple); }
.tips-stat .stat-value { color: var(--accent-red); }
.hero-vs { font-size: 1rem; font-weight: 700; color: var(--text-muted); font-style: italic; opacity: 0.5; padding: 0 8px; }
.hero-verdict-box { flex: 1; min-width: 280px; text-align: center; padding: 16px; background: var(--bg-secondary); border-radius: var(--radius-sm); border: 1px solid var(--border); }
.hero-verdict-label { display: block; font-size: 0.75rem; color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; margin-bottom: 8px; font-weight: 600; }
.hero-verdict-detail { font-size: 0.85rem; color: var(--text-secondary); margin-top: 6px; }
#hero-verdict-badge { margin-bottom: 0; font-size: 1.15rem; padding: 8px 24px; }

/* ---- I-Bond Table ---- */
.ibond-table-section { margin-bottom: 24px; }
.ibond-table-section h2 { font-size: 1rem; font-weight: 600; margin-bottom: 4px; }
.section-subtitle { font-size: 0.82rem; color: var(--text-muted); margin-bottom: 14px; }
.table-wrapper { overflow-x: auto; border-radius: var(--radius); border: 1px solid var(--border); }
table { width: 100%; border-collapse: collapse; font-size: 0.85rem; }
thead { background: var(--bg-secondary); }
th { padding: 10px 14px; text-align: left; font-weight: 600; font-size: 0.75rem; text-transform: uppercase; letter-spacing: 0.05em; color: var(--text-secondary); }
td { padding: 10px 14px; border-top: 1px solid var(--border); font-family: var(--font-mono); font-size: 0.82rem; }
.ibond-table tbody tr { cursor: pointer; transition: background 0.15s; }
.ibond-table tbody tr:hover { background: rgba(108,99,255,0.08); }
.ibond-table tbody tr.selected { background: rgba(108,99,255,0.15); }
.ibond-table tbody tr.new-purchase { border-top: 2px solid var(--border); }
td.winner { color: var(--accent-green); font-weight: 600; }
td.spread-pos { color: var(--accent-green); }
td.spread-neg { color: var(--accent-red); }
.table-note { margin-top: 6px; font-size: 0.75rem; color: var(--text-muted); }

/* Verdict badges */
.verdict { display: inline-block; padding: 3px 10px; border-radius: 12px; font-size: 0.72rem; font-weight: 600; font-family: var(--font-sans); letter-spacing: 0.03em; }
.verdict-hold { background: var(--accent-green-dim); color: var(--accent-green); }
.verdict-switch { background: var(--accent-red-dim); color: var(--accent-red); }
.verdict-wait { background: var(--accent-gold-dim); color: var(--accent-gold); }
.verdict-buy { background: rgba(108,99,255,0.15); color: var(--accent-purple); }
.verdict-comparable { background: var(--accent-gold-dim); color: var(--accent-gold); }

/* Buttons */
.btn-analyze {
  background: var(--accent-purple);
  color: white;
  border: none;
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.85rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}
.btn-analyze:hover {
  background: #7d73ff;
  transform: translateY(-1px);
}
.show-all-btn { display: block; width: 100%; margin-top: 6px; padding: 8px; background: transparent; border: 1px dashed var(--border); border-radius: var(--radius-sm); color: var(--text-secondary); font-family: var(--font-sans); font-size: 0.82rem; cursor: pointer; transition: all 0.2s; }
.show-all-btn:hover { border-color: var(--accent-purple); color: var(--accent-purple); }

/* ---- Detail Panel ---- */
.detail-modal-content {
  width: 90%;
  max-width: 800px;
  max-height: 90vh;
  overflow-y: auto;
  border: 1px solid var(--border);
}

.detail-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 24px;
}
.detail-header h3 { margin: 0; font-size: 1.5rem; }
.detail-close { background: transparent; border: none; color: var(--text-secondary); font-size: 1rem; cursor: pointer; }
.detail-body { padding: 20px; }
.detail-summary {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 16px;
  margin-bottom: 32px;
}
.detail-stat {
  padding: 16px;
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
}
.detail-stat-label { display: block; font-size: 0.8rem; color: var(--text-secondary); margin-bottom: 4px; }
.detail-stat-value { font-size: 1.2rem; font-weight: 600; }
.detail-stat-value.good { color: var(--accent-green); }
.detail-stat-value.bad { color: var(--accent-red); }

.detail-verdict {
  margin-top: 32px;
  padding: 24px;
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  text-align: center;
}

/* ---- Signal ---- */
.signal-badge {
  display: inline-block;
  padding: 8px 24px;
  border-radius: 100px;
  font-weight: 700;
  font-size: 1.1rem;
  margin-bottom: 12px;
  letter-spacing: 0.05em;
}
.signal-badge.buy { background: var(--accent-green); color: #000; }
.signal-badge.sell { background: var(--accent-red); color: #fff; }
.signal-badge.wait { background: var(--accent-gold); color: #000; }
.signal-badge.neutral { background: var(--border); color: var(--text-primary); }
.signal-explanation { color: var(--text-secondary); font-size: 0.85rem; max-width: 600px; margin: 0 auto; }

/* ---- Explainer Page ---- */
.explainer-page { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius); padding: 32px; margin-bottom: 24px; box-shadow: var(--shadow); }
.explainer-page h2 { font-size: 1.5rem; margin-bottom: 24px; color: var(--text-primary); }
.explainer-content { color: var(--text-secondary); font-size: 0.9rem; line-height: 1.7; }
.explainer-content h3 { color: var(--text-primary); font-size: 1.05rem; margin: 24px 0 8px; }
.explainer-content ul { padding-left: 20px; margin-bottom: 16px; }
.explainer-content li { margin-bottom: 8px; }

/* ---- Footer ---- */
footer { text-align: center; padding: 28px 24px; color: var(--text-muted); font-size: 0.75rem; border-top: 1px solid var(--border); }
footer a { color: var(--accent-purple); text-decoration: none; }
footer a:hover { text-decoration: underline; }

/* ---- Responsive ---- */
@media (max-width: 640px) {
  header { padding: 0 16px; height: auto; min-height: 56px; flex-wrap: wrap; gap: 4px; padding-top: 10px; padding-bottom: 10px; }
  .header-inner h1 { font-size: 0.95rem; }
  .top-nav { gap: 0; }
  .nav-btn { padding: 5px 10px; font-size: 0.8rem; }
  .rates-row { flex-direction: column; }
  .detail-summary { grid-template-columns: repeat(2, 1fr); }
  .signal-badge { font-size: 0.95rem; padding: 8px 20px; }
}

/* ─── Multi-page additions ──────────────────────────────────────── */
.brand-link { text-decoration: none; color: inherit; }
a.nav-btn { text-decoration: none; display: inline-block; }

.page-title { font-size: 1.6rem; font-weight: 700; margin: 8px 0 4px; }
.page-intro { color: var(--text-secondary); font-size: 0.95rem; margin-bottom: 20px; max-width: 70ch; }

/* Best day to buy / redeem — slim text row, no card */
.best-day-card {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  padding: 6px 0; margin-bottom: 12px;
}
.best-day-label { color: var(--text-muted); font-size: 0.85rem; }
.best-day-value { font-family: var(--font-mono); color: var(--accent-purple); font-weight: 600; font-size: 0.95rem; }
.tip-btn {
  background: transparent; border: 1px solid var(--border); color: var(--text-muted);
  border-radius: 12px; padding: 2px 10px; font-size: 0.75rem; font-weight: 500;
  font-family: var(--font-sans); cursor: pointer; user-select: none; transition: all 0.15s;
}
.tip-btn:hover { background: var(--bg-card); color: var(--text-secondary); }
.tip-popup {
  position: absolute; z-index: 200;
  background: var(--bg-secondary); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 10px 14px;
  font-size: 0.82rem; color: var(--text-secondary); max-width: 300px; line-height: 1.5;
  box-shadow: var(--shadow); opacity: 0; pointer-events: none;
  transform: translateY(-4px); transition: opacity 0.15s, transform 0.15s;
}
.tip-popup.visible { opacity: 1; pointer-events: auto; transform: translateY(0); }

/* Handoff card (cross-page CTA) */
.handoff-card {
  display: block; text-decoration: none; margin: 28px 0;
  background: var(--bg-card); border: 1px solid var(--border);
  border-radius: var(--radius-sm); padding: 18px 20px; transition: all 0.2s;
}
.handoff-card:hover { background: var(--bg-card-hover); border-color: var(--accent-purple); box-shadow: 0 0 12px var(--accent-purple-glow); }
.handoff-card strong { display: block; color: var(--text-primary); font-size: 1rem; margin-bottom: 2px; }
.handoff-card span { color: var(--accent-purple); font-size: 0.9rem; font-weight: 500; }

/* FAQ */
.faq-list { margin-bottom: 32px; }
.faq-item { background: var(--bg-card); border: 1px solid var(--border); border-radius: var(--radius-sm); margin-bottom: 10px; padding: 4px 18px; }
.faq-item summary { cursor: pointer; font-weight: 600; padding: 12px 0; list-style: none; }
.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::before { content: '+'; color: var(--accent-purple); font-weight: 700; margin-right: 10px; }
.faq-item[open] summary::before { content: '−'; }
.faq-item p { color: var(--text-secondary); padding: 0 0 14px 0; max-width: 75ch; }
.faq-item a { color: var(--accent-purple); }

/* Breadcrumb (per-era pages) */
.breadcrumb { font-size: 0.85rem; color: var(--text-muted); margin-bottom: 1.25rem; }
.breadcrumb a { color: var(--accent-purple); text-decoration: none; }
.breadcrumb a:hover { text-decoration: underline; }

/* Footer nav */
.footer-nav { margin-top: 8px; font-size: 0.85rem; color: var(--text-muted); }
.footer-nav a { color: var(--text-secondary); text-decoration: none; }
.footer-nav a:hover { color: var(--accent-purple); }